Narrative:

We received an EICAS message 'tire pressure' about 15 mins after takeoff. Over the course of approximately 30 mins the #9 tire pressure dropped to 1 psi. Upon consulting with maintenance; we may have had a tire or sensor failure. The consequences of a flat tire were no autobrakes; and therefore no autoland. Landing was uneventful and no problems were noted. Braking was not used until slowing to taxi speed. A post inspection of the #9 tire revealed a totally delaminated tire with numerous large rubber pieces hanging from the truck. Damage from a flat tire can range from minor to catastrophic. This aircraft was removed from service for the damage. The rather innocuous message 'tire pressure' doesn't seem to accurately reflect the possible results of a flat or blown tire. During the descent with spoilers fully extended; autoplt engaged; autothrottles at idle; VNAV engaged (VNAV speed); IAS 315 KTS; the aircraft suddenly and inexplicably overspd the barberpole. I immediately disengaged the autoplt and smoothly raised the nose to decrease the speed. Before the event we had a 60 KT tailwind and immediately after the event we noticed a 35 KT headwind. The ground speed remained relatively constant throughout. We suspect the 10 KT buffer the airplane maintains from the high speed warning was insufficient to deal with the sudden wind shift quick enough to prevent the inadvertent overspd.

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Original NASA ASRS Text

Title: B777 CAPTAIN REPORTS ENCOUNTERING SHARP WIND SHEAR WHILE DESCENDING THAT CAUSES AN OVER SPEED WARNING. HE ALSO REPORTS DAMAGE CAUSED BY LANDING WITH A FLAT TIRE AFTER IT LOST PRESSURE ENROUTE.

Narrative: WE RECEIVED AN EICAS MESSAGE 'TIRE PRESSURE' ABOUT 15 MINS AFTER TKOF. OVER THE COURSE OF APPROX 30 MINS THE #9 TIRE PRESSURE DROPPED TO 1 PSI. UPON CONSULTING WITH MAINT; WE MAY HAVE HAD A TIRE OR SENSOR FAILURE. THE CONSEQUENCES OF A FLAT TIRE WERE NO AUTOBRAKES; AND THEREFORE NO AUTOLAND. LNDG WAS UNEVENTFUL AND NO PROBS WERE NOTED. BRAKING WAS NOT USED UNTIL SLOWING TO TAXI SPD. A POST INSPECTION OF THE #9 TIRE REVEALED A TOTALLY DELAMINATED TIRE WITH NUMEROUS LARGE RUBBER PIECES HANGING FROM THE TRUCK. DAMAGE FROM A FLAT TIRE CAN RANGE FROM MINOR TO CATASTROPHIC. THIS ACFT WAS REMOVED FROM SVC FOR THE DAMAGE. THE RATHER INNOCUOUS MESSAGE 'TIRE PRESSURE' DOESN'T SEEM TO ACCURATELY REFLECT THE POSSIBLE RESULTS OF A FLAT OR BLOWN TIRE. DURING THE DSCNT WITH SPOILERS FULLY EXTENDED; AUTOPLT ENGAGED; AUTOTHROTTLES AT IDLE; VNAV ENGAGED (VNAV SPD); IAS 315 KTS; THE ACFT SUDDENLY AND INEXPLICABLY OVERSPD THE BARBERPOLE. I IMMEDIATELY DISENGAGED THE AUTOPLT AND SMOOTHLY RAISED THE NOSE TO DECREASE THE SPD. BEFORE THE EVENT WE HAD A 60 KT TAILWIND AND IMMEDIATELY AFTER THE EVENT WE NOTICED A 35 KT HEADWIND. THE GND SPD REMAINED RELATIVELY CONSTANT THROUGHOUT. WE SUSPECT THE 10 KT BUFFER THE AIRPLANE MAINTAINS FROM THE HIGH SPD WARNING WAS INSUFFICIENT TO DEAL WITH THE SUDDEN WIND SHIFT QUICK ENOUGH TO PREVENT THE INADVERTENT OVERSPD.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.